The present invention relates to power steering pumps for motor vehicles and, more specifically, to a motor vehicle power steering pump having a cooling jacket cooled by a liquid cooling system of the vehicle.
Conventional internal combustion engines produce heat that must be removed from the engine. Most vehicles employing an internal combustion engine also employ a liquid cooling system to remove the heat generated by the engine. The liquid used for this purpose is generally a mixture of water with ethylene glycol added to inhibit corrosion in the system and permit operation at cold temperatures. A typical cooling system includes tubing or hoses to transfer the liquid coolant from the engine to a radiator or heat exchanger, wherein the liquid is cooled by air flow through the radiator, the cooled liquid exiting the radiator is then pumped by a separate fluid pump through tubing or hoses in a return path to the engine.
Motor vehicles also commonly employ power steering assist systems in order to reduce the amount of effort required to steer the vehicle. These systems generally employ a power steering pump fluid, such as a hydraulic fluid, which is pumped within a steering control unit. The pumping pressure is used to assist steering effort of the vehicle. In use, the power steering pump generates heat, which is normally removed by another heat exchange system. Known systems to remove heat from the power steering pump use an air-cooled heat exchanger wherein the fluid from the hydraulic pump system is transferred and air-cooled in the heat exchanger in a manner similar to the liquid cooling that takes place in a radiator for the engine coolant.
Vehicle operating conditions can effect the flow rate of cooling air to the power steering system heat exchanger, which then affects the heat exchange rate and therefore the performance of the overall system. A vehicle is often required to travel in a stop-and-go fashion, particularly when commuting in heavily populated areas. In warm weather, heat generated by the power steering pump is continuously transferred to the heat exchanger. When the vehicle is stopped for extended periods of time, however, the heat exchanger does not receive sufficient air flow to cool the power steering fluid. During cold weather, an opposite effect occurs. Cold temperatures increase the viscosity of the power steering pump fluid. As the temperature of the air flow through the heat exchanger decreases, the power steering pump fluid will become increasingly viscous, thereby reducing its lubricating capability. Increased wear on the pump""s moving components can result from the flow of higher viscosity fluid through the pump. Also, during low temperature operation, a high frequency noise is often generated by the power steering pump. This noise is also a result of increased power steering fluid viscosity.
In addition to the above temperature considerations, the power steering pump and its heat exchanger provide both arrangement and cost difficulties to overcome. As a separate component, the heat exchanger must be mounted and provided with fluid hoses and/or tubing for transfer between the pump and the heat exchanger. Arrangement of components on many motor vehicles is constrained; therefore, the requirement to provide an individually mounted heat exchanger as a separate component to provide cooling for the power steering pump increases the overall cost and weight of the vehicle.
Systems that employ the engine coolant from the motor vehicle to cool the power steering fluid for the power steering system are known. Such systems transfer the power steering fluid from the pump to a heat exchanger, wherein the engine coolant from the motor vehicle cools the power steering fluid flowing there through. Also known are systems that employ the engine coolant itself as the fluid to actuate the power steering pump unit. Coolant actuating systems require a pressure control sub-system, because the hydraulic power steering system operates at a higher pressure than the pressure of the engine coolant system. The disadvantage of known engine coolant systems employed to separately cool the fluid from the power steering system is that a separate heat exchanger is employed. Engine coolant provided to operate the power steering pump can also cool the pump; however, the disadvantage of employing engine coolant for this purpose is that pressure control components are added to increase the normally lower engine coolant pressure, which increase the system weight, cost and arrangement complexity.
In accordance with one embodiment of the present invention, a power steering pump is provided which comprises a power steering pump housing having an open end and an integral cooling jacket for circulating a coolant to cool the pump housing. An end cover sealably covers the housing open end.
In another embodiment of the present invention, a motor vehicle cooling system is provided. The system comprises an engine and a radiator in fluid communication with the engine via a coolant return line. The radiator cools an engine coolant prior to return of the coolant to the engine through the coolant return line. A fluid pump in fluid communication with the radiator pumps the engine coolant from the radiator to the engine. A power steering pump includes a pump housing and a cooling jacket. The cooling jacket is disposed about the pump housing and is connected with the coolant return line to provide engine coolant to the power steering pump, wherein the coolant flows between the cooling jacket and the pump housing to cool the power steering pump.
In a further embodiment of the present invention, a method is provided to cool a power steering pump of a motor vehicle. The method comprises the steps of pumping an engine coolant through a coolant system of a motor vehicle, disposing a power steering pump having a pump housing in fluid communication with the coolant system, arranging a cooling jacket about the pump housing, and circulating the engine coolant between the cooling jacket and the pump housing to cool the power steering pump.
It is desirable to provide the engine coolant to the hydraulic power steering pump after the coolant has exited the heat exchanger or radiator of the motor vehicle. A connection is provided downstream of the radiator to supply the inlet flow to the cooling jacket. Engine coolant flow enters an inlet port of the cooling jacket, flows through the jacket, and exits through an exit port where the coolant is returned to the engine coolant system.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.